Assessing the Nature of the Distribution of Localised States in Bulk GaAsBi

Abstract

A comprehensive assessment of the nature of the distribution of sub band-gap energy states in bulk GaAsBi is presented using power and temperature dependent photoluminescence spectroscopy. The observation of a characteristic red-blue-red shift in the peak luminescence energy indicates the presence of short-range alloy disorder in the material. A decrease in the carrier localisation energy demonstrates the strong excitation power dependence of localised state behaviour and is attributed to the filling of energy states furthest from the valence band edge. Analysis of the photoluminescence lineshape at low temperature presents strong evidence for a Gaussian distribution of localised states that extends from the valence band edge. Furthermore, a rate model is employed to understand the non-uniform thermal quenching of the photoluminescence and indicates the presence of two Gaussian-like distributions making up the density of localised states. These components are attributed to the presence of microscopic fluctuations in Bi content, due to short-range alloy disorder across the GaAsBi layer, and the formation of Bi related point defects, resulting from low temperature growth.

Increasing Optical Efficiency in the Telecommunication Bands of Strain-Engineered Ga(As,Bi) Alloys

“…In both cases, we find, together with the main component due to Ga-Bi bound [Bi(1)], a higher binding energy component [Bi (2)] with a low intensity that is likely due to Bi-Ga-Bi complexes. for the standard compressive samples C1, C2, and C4, appears redshifted with respect to the expected free exciton [27][28][29][30][31]. Such a redshift is well known in this material and is explained by the presence of Bi-related localized states close to the valence-band maximum (VBM), which dominates the exciton recombination processes at low temperatures.…”

Exciton localization and structural disorder of GaAs1−xBix/GaAs quantum wells grown by molecular beam epitaxy on (311)B GaAs substrates

“…However, the effects of exciton localization, due to alloy disorder and potential fluctuations, result in a temperature dependence of the PL peak position which cannot be explained by the standard Varshni's model 38 . This effect is probably due to the well-known "S-shaped" behavior of disordered semiconductors including GaAsBi 29,32,37,39 . At higher temperatures and for higher P EXC the PL spectra are expected to be dominated by free excitons [35][36][37] .…”

GaAs1-xBix growth on Ge: anti-phase domains, ordering, and exciton localization

“…Photoluminescence properties. The photoluminescence properties of GaAsBi have been a subject of numerous studies 11,12,[53][54][55][56] . Notable PL features of the bismide include a broad PL peak at room temperature, a red-blue-red shift of the temperature-dependent PL peak-energy position, integrated PL intensity plateau at intermediate temperatures, and the saturation of the Stokes-shift at elevated excitation powers.…”